In a wireless cellular communication system, discussion on a transmission/reception method capable of reducing latency as much as possible is in progress. In particular, according to the method, data is transmitted as soon as possible within a short time period using a short TTI (transmission time interval) for a service/UE sensitive to latency and a response is transmitted within a short time period in response to the data. On the contrary, it is able to transmit/receive data using a longer TTI for a service/UE less sensitive to latency. For a service/UE sensitive to power efficiency rather than latency, it may be able to repeatedly transmit data using the same low power or transmit data by more extending a TTI. And, a method of performing transmission and reception on an unlicensed band rather than a frequency band of a legacy communication system has been introduced in a wireless cellular communication system.
When a wireless cellular communication system of a short TTI is introduced, the present invention proposes a method of performing uplink transmission on an unlicensed band.